Protection device for electric circuits.



H. DEF. ARNOLD.

PROTECTION DEVICE FOR ELECTRIC CIRCUITS.

APPL ICATION FILED DEC.14, I914.

1 168,270. Patented Jan. 18, 1916.

W/fflesses: //7 ve "for:

"UNITED STATES PATENT OFFICE.

HAROLD DE FOREST ARNOLD, OF EAST ORANGE, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPAN Y, INCORPORATED,A CORPORATION OF NEW YORK.

ted to a receiving circuit. Its object is to provide means whereby no power in excess of a predetermined value can be transmitted to-the protected circuit, however high the applied voltage may be. This object is accomplished by making use of the fact that two unilaterally conducting elements in series opposition in a circuit limit the current which may flow in either direction around that circuit. In order, however, that this limiting value shall not be zero, some current must flow in each element, and this flow is provided for. by supplying the elements with direct current from a source of electromotive force in a local circuit. Such a circuit will be a direct current shunt on each element, but by inserting a choke coil 1n series with the source of electromotive force in the local circuit, this path is made to have a high impedance t0 the alternating current which it is desired to transmit.- The amplitude of the alternating current which may be transmitted is therefore limited to the value of the direct current used to polarize the elements.

The invention consists in two electric valves, each consisting of an electron-emitting cathode and an anode inclosed in an evacuated tube, connected in multiple to a source of constant electromotive force applied to the valves in the usual direction so as to make the heated elements the cathodes, and in connecting the cathodes of the valves to a winding of one transformer and the anodes to a winding of another transformer, the other windings of the transformers including, respectively, circuits which are thus so inductively connected that power in excess of a given value cannot be transmitted from one of said circuits to the other.

The invention may be more readily under stood by reference to the accompanying drawing which illustrates the preferred embodiment of the invention.

PROTECTION DEVICE FOR ELECTRIC CIRCUITS.

Specification of Letters Patent. Patented Jan. 18, 1916.

A plication filed December 14, 1914. Serial No. 877,056.REISSUED Referring to the drawings, 1, 1 are two vacuum tubes, each of which incloses a heated filament 2 and an electrode 3. The

'filament 2 is heated in the usual manner from the battery 4. These electric valves are connected in multiple to a battery 5 or other suitable source of constant electromotive force, so applied to the valves that the filament 2 becomes the cathodeandthe electrode 3 the anode. The currents through the valves must be slightly greater than themaximum value of the alternating current which it is desired to transmit. The cathode 2'is an electron-emitting cathode preferably of the type known as Wehnelt cathode. The anode 3 may be an electrode of any suitable .kind, as for example, a metallic plate. Such vacuum tube device has the well known property of acting as a valve, permitting the flow of current in onedirection and not in the other, that is to say, when the filament is heated to incandescence current ment is the cathode.

The cathodes 2, 2 are connected to the opposite terminals of a winding 6 of a transof the winding 8.

The winding 10 of the transformer-7 and I the winding 11-of the transformer 9 are in- 'fiows through the tube only when the filawinding 6, an electric valve land one-half i cluded in the circuits 12 and 13, respectively,'

which are thus inductively connected through the transformers 7 and 9 and at the by the valves with negligible distortion. It

is, however, impossible to pass through the circuit in either direction an alternating current ofamplitude greater than that of a the steady direct current through the valves,

same time protected against abnormal power since this would require a flow of current from the cathode to the anode in one of the valves, in which direction current cannot pass. In other words the alternating current in the valve circuit is equal to the variation in direct current through the valves, since the high inductance chcke coil prevents the flow of alternating current in the battery branch, and therefore themaximum alternating current is limited by the value of that direct current. i

An impedance 14 is introduced in order to prevent the flow of, alternating current through the branch in which the battery is included. Furthermore, some suitable form of arrester 15 may be bridged across the two parallel branches in ,which the electric valves are included, such 'arrester acting to break down when abnormally high voltages are impressed upon the input side, and thus furnishing additional protection.

'What is claimed is:

. 1. In a protector for-electric circuits,'the

combination of a source of direct potential two electric valves connected in multiple to said source of potential, each valve consistmg of an electron-emitting cathode and an anode inclosed in an evacuated tube; windlngs connecting, respectively, said anodes and said cathodes; and two circuits inductively connected, respectively, to said windmgs.

2. In a protector for electric circuits, the combination of two electric valves each consisting of an electron-emitting cathode and I an anode inclosed in an evacuated tube; two

transformers one winding of each of which an evacuated-vessel, transformer windings.

for connecting together said anodes and said cathodes, respectively, and other windings of said transformers for connecting said protector to said source of power and to said receiving circuit.

4. 1n combination with a source of power and a receiving circuit, a protector for electric circuits comprising a source of constant electromotive force, an inductive branch containing such'source, uhilaterally conducting thermionic elements connected in multiple to such branch, transformer windings for connecting said elements in multiple and other windings of said transformers for connecting said protector to said source of'power' and to said receiving circuit.

In witness whereof, I hereunto subscribe my name this 12th day of December, A. D. 1914:.

HAROLD DE FOREST ARNOLD.

Witnesses:

E. EDLER, K. L. ST'AHL. 

